1. Field of the Invention
The present invention generally relates to a method for fabricating devices on semiconductor substrates. More specifically, the present invention relates to a method of fabricating quantum features on a semiconductor substrate.
2. Description of the Related Art
Microelectronic devices are generally fabricated on a semiconductor substrate as integrated circuits wherein various conductive layers are interconnected to one another to facilitate propagation of electronic signals within the device. An example of such a device is a storage element in silicon nano-crystal based nonvolatile memories.
In such memories, the charge is stored in an array of spaced apart small islands (or quantum dots) of silicon. The array of such quantum dots forms a floating gate that may be embedded in a gate dielectric of a gate structure of a field effect transistor. Generally, about 500-700 quantum dots are used to form one floating gate. A quantum dot is generally a silicon structure having topographic dimensions on order of 10's of nanometers.
Quantum features are also used as semiconductor lasers. Recently, such quantum dots, when released from the substrate, have also found a use in non-semiconductor applications, for example, as carriers of precursors, inhibitors, and the like in chemical reactions performed between liquid phase reactants.
In a floating gate field effect transistor fabrication process, a lithographically patterned mask is used during etch and deposition processes that form the gate structure of the transistor. As topographic dimensions of transistors continue decreasing in advanced integrated circuits, conventional lithographic techniques become unable to accurately define components of the gate structure and, specifically, the quantum dots of the floating gate of the gate structure of ever-smaller transistors.
Therefore, there is a need in the art for an improved method of fabricating silicon quantum dots and other forms of quantum features.